1. Field of the Invention
The present invention relates to a connective structure for steel frame columns and steel frame girders built of H beams.
2. Description of the Related Art
Known connective structures for H beam-built steel frame columns and steel frame girders include one which uses T-shaped fittings, so-called split Ts, as described in JP-A-07-102635 cited below. According to JP-A-07-102635, the flange parts of each connective fitting have plural bolt inserting holes, an inclined face is formed from the bolt inserting holes of the connective fittings in contact with steel frame columns toward their ends, and the flange parts are tension-connected to the steel frame columns by fastening with high strength bolts pressed through the bolt inserting holes in a state of being held in contact with the flange parts of the steel frame columns. On the other hand, the web part of each connective fitting has plural bolt inserting holes, and the web parts are connected to steel frame girders by fastening with high strength bolts pressed through the bolt inserting holes in a state of being held in contact with the flange parts of the steel frame girders. The connective fittings according to JP-A-07-102635, when tensile forces work on them to subject the flange parts of the connective fitting to bending deformation, turn pivoting on the bolt inserting holes in contact with the flange parts of the steel frame columns and accordingly no reaction of lever works, enabling the tensile stress to be eased.
There is also known what uses racket-shaped connective fittings, so-called paddle bolts, as disclosed in JP-A-59-85051 cited below. According to JP-A-59-85051, each connective fitting has a bolt part at one end and the other end forms a planar part having a bolt inserting hole. The bolt parts of the connective fittings are pressed through the bolt inserting holes bored in the flange parts of steel frame columns and fastened to be tension-connected to the steel frame columns. On the other hand, the planar parts of the connective fittings are connected to steel frame girders by being fastened with high strength bolts pressed through the bolt inserting holes in a state of being in contact with the flange parts of the steel frame girders. With the connective fittings of JP-A-59-85051, even if the plumbing accuracy of the steel frame columns is somewhat poor, dimensional adjustment can be accomplished by turning adjustive nuts screwed onto the bolt parts, making it possible to facilitate the operation and improve workability.
However, the conventional connective fittings used in the connective structures described above involve a problem that they have no sufficient yield strength against tensile, compressive and shearing forces. Especially, the web parts of split Ts and the bolt parts provided at one end each of paddle bolts are poor in yield strength against tensile and compressive forces working in the rectangular direction, involving a problem that these parts may be broken even before the tensile and compressive forces reach the web parts of steel frame columns. There is another problem that, since the connective fittings are connected on the flange parts of steel frame columns, forces from the steel frame columns are always transmitted via the flange parts of the steel frame columns. Thus, the flange parts of steel frame columns become even poorer in yield strength against the tensile and compressive forces working on them in the rectangular direction in the farther areas from the central position in their shorter side direction and, if excessively high tensile and compressive forces are transmitted to the flange parts of the steel frame columns via the connective fittings, not only the connective fittings but also the flange parts of the steel frame columns may be broken in this area. These circumstances are leading to a trend of making the connective structure greater in yield strength by building connective fittings such as split Ts and paddle bolts, tightening items such as bolts and nuts, and constituent members of steel frame columns such as flange parts of high strength steel and/or designing them greater in thickness and diameter, but the loss of yield strength due to bolt inserting holes and the like has also to be made up for, resulting in the need to use plural reinforcing members including gusset plates and reinforcing steel plates. As a consequence, the manufacturing cost of constituent members as well as the working cost and carriage cost resulting from the increased number of constituent members are rising, also entailing delays in construction schedules.
An object of the present invention, attempted in view of the above-noted problems found in conventional structures, is to provide a connective structure for steel frame columns and steel frame girders which can achieve sufficient yield strength against tensile, compressive and shearing forces working on the steel frame columns and the steel frame girders with simply configured connective fittings and contribute to reducing costs and construction periods.